Dyes and coloring agents have been used for a variety of purposes throughout history. For example, green copper salts extracted from mines were used as an eye shadow by the Egyptians as early as 5000 B.C. Similarly henna was and is still used as a hair and fingernail colorant in the Middle East, Asia and other parts of the world. A variety of plant and animal dyes were used to dye textiles, and certain colors were valued more highly than others. See R. A. Donkin, The Insect Dyes of Western and West-Central Asia, Anthropos, Herausgeber Anthropos-Institut, 5205 St. Augustin, Deutschland. Vol. 72 1977. Currently, colors are used extensively in textiles, foods, drugs and cosmetics.
The coloring of foodstuffs and condiments dates back at least 500 years. In general, colors are added to food products to improve appearance. Some food producers believe that the color of a food product is more influential with consumers than its flavor. To consumers, off-color foods mean inferior products. Additionally, color may be added to make a food recognizable or to compensate for color loss during food processing.
Until the middle of the nineteenth century, most of the colorants used in food, drugs and cosmetics were from natural sources.
One problem with the natural pigments found in plants or animals is their relative instability. Changes or deviation from natural conditions of these products can bring physical and chemical changes to the color of these products. These factors can include pH alterations or the effect of light or temperature, particularly in the thermal processing necessary to preserve some products over an extended period of time such as two to three years.
A good example of this instability is the class of anthocyanin pigments found in cherries. These pigments are not totally fixed to the fruit, and are additionally susceptible to thermal degradation during canning. Therefore, when mixed with other fruits as in a fruit cocktail, the cherries will bleed and color the syrup and other fruits in the cocktail mixture. After heat treatment, the pigments can fragment and lose their original color, thus resulting in a discolored mixture. As a result, cherries to be used in other products are generally bleached of their natural color and redyed using a more stable dye. Bleaching is usually accomplished by the use of sulfur dioxide, which is then removed with a sodium chlorite solution. Beavers and Payne, Food Technology 23, 175 (1969). Alternatively, the sulfur dioxide may be removed by boiling the cherries.
The instability of these pigments led to the development of synthetic colors. The first synthetic dye was synthesized by a British chemist in 1856. Addition of the first synthetic dye to foods was allowed first for dairy products in the United States; colors were allowed in 1886 for butter and in 1896 for cheese. By the year 1900, synthetic colorants were used in a wide range of foods such as ice cream, candy, ketchup, jellies, noodles, wine and many more.
The effect of synthetic colorants on human health was first recognized in the 1950s, when animal studies were conducted that implicated some colorants as health concerns. As a result, some colorants are no longer permitted in food.
Of particular interest to the present invention is the status of red colors allowed in foods. Within the last thirty years at least four different FD&C Red colors have been delisted by the U.S. Government and are no longer permitted in food.
FD&C Red No. 3 is a Xanthene dye with a range of application from lipstick to candy to dyed cherries. It has a maximum absorbency wavelength at about 520 nm, and is chemically very stable. It precipitates under acidic conditions. However, in January of 1990, the Food and Drug Administration announced the formal banning of FD&C Red No. 3 in cosmetics, based on the required compliance with the Delany Clause of the Food, Drug and Cosmetic Act. This ban, however, does not yet disapprove "permanently" listed uses of the food dye from ingested drugs and foods.
FD&C Red No. 40 will color cherries, but will bleed if the cherries are washed since it doesn't precipitate; this can cause discoloration in cherry ice cream or the pears or syrup in a fruit cocktail mixture. Thus safe but stable alternatives are needed to replace the use of FD&C Red No. 3 in foods.
Carmine is a natural deep red pigment which is approved for use in foods in the United States. The coloring agent in carmine is carminic acid, which is a natural anthraquinone dye. The source of carminic acid is cochineal, which is derived from female insects (Coccus cacti) that live on a particular species of cactus, Nopalea coccinelliferna. The female insects are collected just prior to egg-laying, since the highest concentration of cochineal is in the egg yolks. After the insects are dried and ground, they can be used as is or processed to produce a water soluble cochineal extract or carmine.
Since carmine, cochineal and carminic acid are from the same origin, the word "carmine" will be used to designate any of these three.
The use of carmine in the coloring of food has not been extensive due to the cost of the pigment. Carmine is the most heat stable of the natural red pigments. It also precipitates under acidic conditions. However its use has generally been confined to a utilization of the water soluble form to uniformly color a product, or to produce water soluble sugar syrups that can be used to color foods (Japanese Patent No. 2 386/71) or other products, because of its tendency to bleed. The use of carmine to dye cherries used in fruit cocktail has been previously reported; however the process utilized and the resulting stability of the color are unknown. Tri Valley Growers press release.
Structurally, carmine is similar to other anthraquinones such as alizarin, erytholaccin, deoxyerythrolaccin, laccaic acid, kermesic acid and its isomer ceroalbolinic acid. Of these, only laccaic acid, which is the principal coloring agent of lac dye, is currently used as a dye, although all are chromophores. Lac dye is widely used in Asia and in particular Japan, but is not approved as a food colorant in the U.S.
Anthraquinones are known to form insoluble metal complexes with multivalent metal ions. Commonly, anthroquinones form chelates with metal ions. For example, alizarin is known to form insoluble metal chelates with aluminum and calcium ions to form a dye known as "Turkey Red", a historically important textile dye. Kiel et al. J. Soc. Dyers, Col. 79, 21 (1963a). Alizarin may also form metal complexes with potassium, sodium, tin, iron and chromium ions as well. Kiel et al. J. Soc. Dyers, Col. 79, 62 (1963b). Carmine also forms these insoluble chelate complexes with metal ions, see FIG. 1. Meloan et al. Histochemie 37, 87 (1971).
Calcium ions also are known to play an important part in cellulosic food processing since calcium is a firming agent and increases the thermal tolerance of these foods during thermal processing.